This invention relates to coated articles that have approximately the same color characteristics as viewed by the naked eye before and after heat treatment (e.g., thermal tempering), and corresponding methods. Such coated articles may be used in insulating glass (IG) units, vehicle windows, and/or other suitable applications.
The need for color matchability of coated articles (before heat treatment vs. after heat treatment) is known. Glass substrates are often produced in large quantities and cut to size in order to fulfill the needs of a particular situation such as a new multi-window and door office building, vehicle window needs, etc. It is often desirable in such applications that some of the windows and/or doors be heat treated (i.e., tempered, heat strengthened or bent), while others need not be. Office buildings often employ IG units and/or laminates for safety and/or thermal control. It is often desirable that the units and/or laminates which are heat treated (HT) substantially match their non-heat treated counterparts (e.g., with regard to color, reflectance, and/or the like) for architectural and/or aesthetic purposes.
U.S. Pat. No. 5,376,455 discloses a coated article including: glass/Si3N4/NiCr/Ag/NiCr/Si3N4. Unfortunately, the coating system of the ""455 patent is not sufficiently color matchable after heat treatment with its non-heat-treated counterpart. In other words, the coating system of the ""455 patent has a rather high xcex94E value. This means that, unfortunately, two different coated articles with different coatings (one to be heat treated, the other not to be) must be made for customers who want their heat-treated and non-heat-treated coated articles to approximately match colorwise as viewed by the naked eye.
As with the ""455 patent, it has mostly been possible to achieve matchability only by providing two different layer systems, one of which is heat treated (HT) and the other is not. The necessity of developing and using two different layer systems to achieve matchability creates additional manufacturing expense and inventory needs which are undesirable.
However, commonly owned U.S. Pat. No. 5,688,585 discloses a solar control coated article including glass/Si3N4/NiCr/Si3N4, wherein matchability is achieved with a single layer system. As explained at column 9 of the ""585 patent, it is a xe2x80x9crequirementxe2x80x9d of the ""585 invention that the NiCr layer be substantially free of any nitride. An object of the ""585 patent is to provide a sputter coated layer system that after heat treatment is matchable colorwise with its non-heat-treated counterpart. However, the ""585 patent uses a heat treatment (HT) of only three (3) minutes (col. 10, line 55). Longer heat treatments are often desired in order to attain better tempering or HT characteristics. Unfortunately, as explained below, it has been found that with longer HT times the coatings of the ""585 patent cannot maintain low xcex94E values and thus lose color matchability. In particular, it has surprisingly been found by the instant inventor that in coatings such as that of the ""585 patent, xcex94E values jump significantly upward after HT for 4-5 minutes at a temperature of from about 600 to 800 degrees C.
Consider the following layer stack (see Example 7 below): glass/Si3N4/NiCr/Si3N4, where the underlayer of Si3N4 is about 50-70 xc3x85 (angstroms) thick, the NiCr layer is about 325 xc3x85 thick (the NiCr layer is not nitrided as deposited as can be seen in FIG. 15), and the overcoat of Si3N4 is about 210-310 xc3x85 thick. As explained in Example 7 below, this coated article has a rather high transmissive xcex94E* value of about 5.9 after a heat treatment (HT) at 625 degrees C. for ten (10) minutes. This high transmissive xcex94E value means that a HT version of the ""585 coated article does not approximately match colorwise non-heat-treated counterpart versions with regard to transmissive color after 10 minutes of HT. This is not desirable.
The instant inventor believes that the high xcex94E* value associated with the coating of Example 7 herein is caused for at least the following reasons. FIG. 15 is an XPS plot illustrating the Example 7 coating before heat treatment (HT), while FIG. 16 illustrates the Example 7 coating after HT. As shown in FIG. 15, before heat treatment the three different layers are fairly separate and distinct. For example, prior to HT it can be seen that the Ni slopes 3 on either side of the NiCr layer are very steep, as are the Si and N slopes 5 and 7, respectively, on the lower side of the upper Si3N4 layer. Therefore, the vast majority of the Ni is located in the NiCr layer and the vast majority of the Si and N from the upper Si3N4 layer is located in that layer. However, FIG. 16 illustrates that when the FIG. 15 coated article of Example 7 is heat treated (HT) for 10 minutes as discussed above, a significant portion of the Ni from the NiCr layer migrates into the upper Si3N4 layer. Additionally, upon HT a significant portion of the Si and N from the upper Si3N4 layer migrates into the NiCr layer. In other words, the interface between the metal NiCr layer and the upper Si3N4 layer becomes blurred and non-distinct. This is evidenced in FIG. 16 by the less steep slope 3a of the Ni on the upper/outer side of the NiCr layer, and by the less steep slopes 5a and 7a of the Si and N on the lower side of the upper Si3N4 layer. Still further, it can be seen by comparing FIGS. 15 and 16 that HT causes a significant amount of the Cr in the NiCr layer to migrate within that layer toward the upper side thereof so that it is not as uniformly distributed compared to pre-HT.
Unfortunately, the aforesaid migrations of the Si, N, Ni and Cr from their FIG. 15 positions to their respective FIG. 16 positions due to HT causes significant color shifting to occur and thus explains the large transmissive xcex94E* value associated with the coating of Ex. 7, and thus with coatings of the ""585 patent when exposed to lengthy heat treatments.
In view of the above, it will be apparent to those skilled in the art that there exists a need for a coating or layer system that has a low xcex94E (or xcex94E*) value(s) (transmissive and/or glass side reflective) and thus good color matchability characteristics after at least five (5) minutes of heat treatment (HT). It is a purpose of this invention to fulfill the above-listed need, and/or other needs which will become more apparent to the skilled artisan once given the following disclosure.
An object of this invention is to provide a coating or layer system that has good color stability (i.e., a low xcex94E* value(s)) with heat treatment (HT).
Another object of this invention is to provide a coating or layer system having a xcex94E* value (transmissive and/or glass side reflective) no greater than 5.0 (more preferably no greater than 4.0, and most preferably no greater than 3.0) upon heat treatment (HT) at a temperature of at least about 600 degrees C. for a period of time of at least 5 minutes (more preferably at least 7 minutes, and most preferably at least 9 minutes).
Another object of this invention is to nitride a Ni and/or Cr inclusive layer (e.g., a NiCr layer) to an extent so as to enable the resulting coated article to have the aforesaid low xcex94E value(s).
Another object of this invention is to fulfill one or more of the above-listed objects.
Generally speaking, certain example embodiments of this invention fulfill one or more of the above listed objects and/or needs by providing a coated article comprising:
a layer system supported by a glass substrate, said layer system comprising a metal nitride inclusive layer located between first and second dielectric layers, wherein the second dielectric layer is at least partially nitrided and positioned so that the metal nitride inclusive layer is between the second dielectric layer and the glass substrate; and
wherein said coated article has a transmissive xcex94E*T value no greater than 5.0 after at least about 5 minutes of heat treatment at a temperature(s) of at least about 600 degrees C.
Certain other example embodiments of this invention fulfill one or more of the above-listed objects and/or needs by providing a coated article comprising:
a layer system supported by a glass substrate, said layer system comprising a metal nitride inclusive layer located between said glass substrate and an at least partially nitrided dielectric layer, wherein the metal nitride comprises at least one of NiNx and CrNx and contacts said dielectric layer; and
wherein said coated article has a glass side reflective xcex94E*G value no greater than 5.0 in view of thermal tempering including heat treating for at least about 5 minutes.
Certain other example embodiments of this invention fulfill one or more of the above-listed objects and/or needs by providing a coated article comprising:
a layer system supported by a glass substrate, said layer system comprising a NiCrNx inclusive layer wherein at least 50% of the Cr is nitrided, said NiCrNx inclusive layer being located between and contacting first and second dielectric layers, wherein the second dielectric layer is at least partially nitrided and positioned so that the NiCrNx inclusive layer is between the second dielectric layer and the glass substrate; and
wherein said coated article has a transmissive xcex94E*T value no greater than 5.0 following or due to heat treatment.
Still further example embodiments of this invention fulfill one or more of the above-listed objects and/or needs by providing a method of making a coated article, the method comprising:
providing a glass substrate;
depositing (e.g., via sputtering or any other suitable method/technique) a metal on the substrate in an atmosphere including a significant amount of nitrogen in order to form a metal nitride inclusive layer on the glass substrate;
depositing (e.g., via sputtering or any other suitable method/technique) a dielectric nitride inclusive layer on the substrate over the metal nitride inclusive layer; and
heat treating the article which includes at least the metal nitride inclusive layer and the dielectric nitride inclusive layer for at least 5 minutes, the metal nitride inclusive layer being nitrided to an extent so that after said heat treating the article has a xcex94E value of no greater than 5.0.